The FDA knows that Glaxo can scale up faster than Sarepta. I think they will get AA but the FDA may be thinking the Glaxo drug works let's get it out there fast. Glaxo never bought Prosensa just the rights to the drug. CG of Sarepta wants to go it alone. Maybe not a good idea.
Does GSK (or any major pharma w "deep pockets") have the expertise to manufacture SRPT's drug? Have you heard CG say, we know how to manufacture it, we just don't have the money to scale up? The breakthrough designation by the FDA doesn't "say" anything about their intention to get one drug out before the other. Maybe reading intentions into an FDA designation is not a good idea?
Drisapersen will be way cheaper than eteplirsen, too. That's mighty attractive. But the bottom line is that the families and the doctors ultimately will choose eteplirsen as their drug of choice because it is safe and effective. Drisapersen is not so safe.